NEW YORK — Just beneath an L train subway platform in Brooklyn, Tanika Gentry fingers the deep green leaves of a collard plant in the black soil of a community garden.

This is dinner.

Gentry, fed up with the spiking cost of food, recently decided to grow her own. Now she is reaping a harvest of collards, cabbages, tomatoes and pumpkins to feed her family.

“Once you have to choose between eating and fuel, there’s nothing greater than going back to the beginning and making your own,” said Gentry, 32, who home-schools her two daughters. “With the way things are going, it may be something a lot more people are realistically doing.”

From Atlanta to Minneapolis to Seattle, people are reacting to the stagnant economy and the high cost of produce by planting their own fruits and vegetables, say garden store owners, bulk seed sellers and industry analysts.

In the skyscrapered canyons of New York City, increasing numbers of people are growing their food on fire escapes, on rooftops, in back yards and in community gardens.

It is a phenomenon that has always ebbed and flowed with the economy, said Bruce Butterfield, the market research director of the National Gardening Association, who has been tracking it for decades. The biggest recent peak in homegrown food came in 1975, during a national oil crisis, he said, when 49 percent of U.S. households were growing vegetables.

Where do gardening, small-scale agriculture and the future of planet Earth converge? For three Washington women, it’s on a road less traveled, on byways unseen from the gotta-get-there, high-speed chaos of the interstate.

It has been a year since Lara Sheets, 26, Liz Tylander, 25, and Kat Shiffler, 24, climbed on their bicycles in Mount Pleasant and pedaled north, eventually to Montreal. Along the way they visited thriving inner-city gardens, innovative suburban farms and rooftop vegetable plots as they chronicled a grass-roots movement seeking to change the way we put food on our table.

The result is a low-budget documentary, “Garden Cycles Bike Tour,” which captures the spirit of their unusual 2,000-mile sojourn and the much larger movement that inspired it. The trip has also generated a Web site and blog, http://womensgardencycles.wordpress.com.

In the course of their three-month odyssey, the women found a community garden in the gutted ghettos of Baltimore, were run off the road by a truck in New Jersey, abandoned efforts to cycle across the Verrazano-Narrows Bridge in New York and got hopelessly lost in New England towns. They slept in the gardens of strangers, discovered new ethnic food and recipes and cemented their desire to change the world by growing vegetables.